This invention relates to a security device and more particularly to an alarm which signals attempted entry to a structure such as ones house via an entry door provided therein. As such, the device is not intended to be a primary lock to prevent entry, but a signal, such that the occupants of the structure may be aware of such attempted entry. The device does however function as a dead bolt lock. It may be also utilized with windows and with sliding, rather than pivotal doors.
Various signal devices to indicate the unauthorized entry into a structure are known and include pressure-sensitive switches which may be placed under carpeting, mats, and the like, or which may be incorporated into a separate wedge-shaped element in turn jammed underneath the bottom of the door or at a point inwardly disposed therefrom, as well as wave-form beams such as a light path which may be interrupted and in turn trigger a signal or alarm. Although generally operable for their intended purposes such devices have inherent drawbacks. For example, the wedge-shaped pressure-sensitive switches may be simply kicked aside by an intruder and the light beam and carpet underlay switches may be avoided by the intruder by his respective movements therebeneath and avoiding walking on entranceway mats and the like.
It is accordingly an object of the present invention to provide a signalling device in combination with a door lock which is of straightforward, relatively simple design, and which can accordingly be sold for a reasonable price and accordingly gain wide consumer acceptance.
A still further object of the present invention is the provision of a door alarm device of the aforementioned type which signals attempted entry by relative, i.e. inward movement of the door with respect to its supporting frame and which is easily adjusted such that even slight inward pressure upon the outside surface of the door triggers the alarm.
Another object of the invention is the provision of a door alarm of the aforementioned type which may be easily deactivated by authorized persons.
These and other objects of the present invention are accomplished by a device adapted for attachment to the inside surface of a door supported for relative, i.e. pivotal movement with respect to a door frame. The device includes a housing and an elongated bolt adapted to slide back and forth with respect to the housing and the door on which it is supported between a first non-activatable position wherein the door may be freely opened and a second activatable position in which attempted opening of the door will trigger the alarm. The bolt is provided with an electrical contact disposed in a spaced position from a similar contact provided in the housing. Spring means are provided so as to normally bias the bolt away from the door and so as to maintain the spaced relationship of the contacts except when such is overcome by door movement accompanying attempted entry such that the contacts engage each other and accordingly activate appropriate electrical circuitry so as to cause the signal to be given, i.e. an audible alarm. In the activatable position of the bolt, one end thereof is engaged by a latch strike mounted on the door frame such that the bolt is held in fixed position with respect to the frame and such that relative movement of the door with respect to the bolt may be achieved. A key-operated assembly including a rotatable finger may be mounted in the door and serve to move the bolt between its first and second positions and thus deactivate the device to authorized persons from the outside of the structure. This deactivation assembly may, however, be purposely overridden by the occupant from the inside of the structure.
Other objects, features, and advantages of the invention shall become apparent as the description thereof proceeds when considered in connection with the accompanying drawings.